Micro vibrations are present in some complicated working environments, and the micro vibrations are key factors that affect machining or working precision of devices. The traditional passive vibration isolator consists of mass-spring-damping elements, but it cannot meet the vibration isolation requirement of precise machining as it has inherent contradictions between the low-frequency vibration transmissibility and the high-frequency vibration attenuation rate. Relative to a passive vibration isolation mechanism, active vibration isolation has greatly improved the performance of the system, but it requires a sensor-actuator pair and a corresponding active control system, which requires the active vibration isolation mechanism to have a simple structure, an efficient algorithm and lower power consumption.
In terms of the structure, the current mainstream micro vibration isolation or suppression devices are formed by connecting passive vibration isolation elements and active actuators in a certain manner. For example, means such as the active and passive composite use of an air spring and a voice coil motor, the active and passive composite use of a diaphragm spring and a voice coil motor, the active and passive composite use of a metal spring and a linear motor, effectively suppress the micro vibrations and have better low frequency and high frequency attenuation capability, but they all have the following problems:
1. Although the active and passive parallel mechanism of the air spring and the voice coil spring causes the vibration isolator to have the advantages of large stroke, high load, low natural frequency and so on, it has a complicated structure and needs to supply air continuously, and the voice coil motor has great power consumption, all of which are not conductive to applications in the space and thus restrict its application to the micro vibration suppression.
2. The active and passive parallel mechanism of the metal spring and the linear motor intends to obtain a lower natural frequency by using a compression spring, which has a higher requirement for the mounting precision and is also relatively difficult in enhancing the control precision.
3. An active vibration isolator designed and applied by employing piezoelectric ceramics as an actuating mechanism has the advantages of high frequency response, high positioning precision and long service life, but it also has the disadvantage of a smaller actuation stroke. Therefore, in practical use, it is often necessary to broaden its effective stroke in combination with technical means, leading to the increase in the cost and inconvenient use.
4. For the field of micro vibration suppression and isolation, wide frequency band and high frequency response are its main characteristics, and the piezoelectric actuator stands out. However, as the active vibration isolation mechanism that employs piezoelectric ceramics as an actuator has greater structural stiffness, it is mostly referred to as a “hard” structure. As a result, the natural frequency of the system is too high, and it is difficult to effectively suppress low-frequency vibrations.
The Patent Document CN102168738B recorded in the State Intellectual Property Patent Office of China discloses a six-degree-of-freedom active and passive dynamic vibration absorbing device, which consists of six motor-actuated single-degree-of-freedom dynamic vibration absorbers, has active and passive control modes and can adapt to multi-degree-of-freedom complicated vibration suppression working conditions, but has special mounting requirements for occasions of use. Moreover, the motion of each degree of freedom requires two vibration absorbers to act at the same time, the requirement for synchronous control precision is higher, and the manufacturing difficulty and the use restriction are greater.